2.2 Experimental plants and substrates
V. natans is a common
submerged macrophyte species, which is widely distributed in the middle
reaches of the Yangtze River. It is widely used for the restoration of
lake ecosystems due to its rapid growth and developed root system, and
it can absorb excess nutrients from the water body (Yan et al. 2013).
The V. natans was incubated in a constant temperature room (25
°C) at a light intensity of 3500 lx with the light-dark duration ratio
of 1:1 for a week. After incubation, the healthy and equal-sized
submerged plants were selected, pruned to a uniform plant height of 10
cm, and transplanted into the polyethylene column (15 cm in diameter,
and 50 cm in height).
The experiments were carried out in polyethylene column with 5 V.
natans plants (10 cm in height) plants in each column containing a
sediment layer of 20 cm thickness. The 4 treatment groups consisted of
maifanite (ME), vermiculite (VE), ceramsite (CE), and volcanic rock
gravels (VR) substrates (3-5mm in particle size). The group without
additional substrate was control group (CK). These substrates all were
produced in Henan province, China. The sediment surface was covered with
15 g substrate to make it 1 cm thick, and then distilled water was added
to make the column water depth reach 24 cm. The experiment was performed
in triplicates. V. natans planting experiment started on June 25,
2022 and lasted for 40 days with plant sampling every 10 days.